In recent years, development of electric vehicles and hybrid electric vehicles using batteries has been earnestly carried out from the consideration of an environment. However, since electric vehicles are still relatively expensive compared to gasoline cars, cost reduction is required, and improvement of energy density is required for secondary batteries as a power source.
In the prior art, as a technology for improving the power density per unit weight of a battery, a technique using a current collector including a polymer material and a conductive filler has been proposed (see Patent Literature 1).